The human eye functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens. When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening is made in the anterior capsule and a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquefies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is then replaced by the IOL.
The IOL is injected into the eye through the same small incision used to remove the diseased lens. An insertion cartridge of an IOL injector is loaded with the IOL, the tip of the insertion cartridge is inserted into the incision, and the lens is delivered into the eye.
Many IOLs manufactured today are made from a polymer with specific characteristics. These characteristics allow the lens to be folded for insertion through a very small incision; the lens unfolds into its proper shape after delivery into the eye. Injector cartridges that fold the lens and provide a relatively small diameter lumen through which the lens may be pushed into the eye, usually by a soft tip plunger, are commonly used. Some of these cartridges are described in U.S. Pat. No. 5,947,976, issued Sep. 7, 1999 to Van Noy et al., and in U.S. Pat. No. 6,537,283, issued Mar. 25, 2003 to Van Noy; the entire contents of each of these patents is incorporated herein by reference. Other cartridges and injector devices are illustrated in U.S. Pat. No. 4,681,102 (Bartell), U.S. Pat. Nos. 5,494,484 and 5,499,987 (Feingold), U.S. Pat. Nos. 5,616,148 and 5,620,450 (Eagles, et al.), U.S. Pat. No. 5,275,604 (Rheinish, et al.), and U.S. Pat. No. 5,653,715 (Reich, et al.) the entire contents of each of these documents are also incorporated herein by reference to provide context and technical background for the disclosure that follows. Notwithstanding the various designs disclosed in these references, improvements in IOL injector cartridges and IOL injection techniques are still needed.